Electromagnetic device with potted coil

Aug. 17, 1965

S. BLANCH! ETAL

ELECTROMAGNETIC DEVICE WITH POTTED Filed Feb. 26, 1960

3,201,729

COIL

Sheets-Sheet 1

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Serge Bianchi Roger Lacour INVENTOR.

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BY

AGENT.

Aug. 17, 1965 s BLANCHI ETAL

ELECTROMAGNETIC DEVICE WITH POTTED

Filed Feb, 26, I960

3,201,729

COIL

Sheets-Sheet 2

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Serge Bianchi Roger Lacour INVENTOR.

^BY

AGENT.

Aug. 17, 1965

S. BLANCHI ETAL

ELECTROMAGNETIC DEVICE WITH POTTED Filed Feb. 26, 1960

3,201,729

COIL

Sheets-Sheet 3

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Serge Bianchi Roger Lacour INVENTOR.

BY

AGENT.

United States Patent Office 3,201,729

----------—_________ Patented Aug. 17, 1965 ίο

3,201,729

ELECTROMAGNETIC DEVICE WITH . POTTED COIL

Serge Bianchi, 48 Ave. Alfred de Musset Le Vesinpf Roger Ue.„, ₈₆ 2¾¾

Filed Feb. 26, I960, Ser. No. 11,272 3 Claims. (CI. 336—83) . Our present invention relates to electromagnetic devices n which _an electric circuit element such as I coH, havffig two or more terminals for connecting it in an external circuit, is provided with one or more ferromragnetic members defining a closed or nearly closed path of high ner Zf¹ L^y/^{Or the magnetic} flux- Devices of this type^nclude, but are not limited to, induction coils relays^rans formers and the stator and rotor portiomffilX motors and generators. ^P electric

It is known to form the cores of electromagnetic coils from compacted comminuted materials of high magnetic permeability, such as ferrites, which are subs” ntiS v non-conductive electrically to minimize the flow of eddy currents m high-frequency applications. The present invention has for its object the utilization of such madevkes o/ fh^P ί ^{the manufacture and} the structure of tvnp f ^{f th}® ^mentioned class, irrespective of the type of current (direct, low-frequency or high-frequency) o be generated or employed in a device of this kind.

n accordance with our present invention we embed able. (preferably insulating) binder, this mass permeate» the interior of the coil and being outwardly shaped into a. mechanical support for the terminals and, if desired for other external elements, such as, for example relav armatures and contact springs. Thus, the ferromagnetic ΪΞηΧί ”⁰¹ “^n,« — » i»”«S termina! base so as positively to interlock therewith upon 40 hardening; also, the body constituted by this mass mav the external . mations to which the externa! elements may be conveniently secured

We have found that the intimate association between the coil and .the ferromagnetic body of an electromagnetic scribp^ei^emb°^{dying theinvention}’ obtained in the aforedscribed manner, considerably increases the efficiency of for lZeXtin^Og.^{reSPOndin8ly itS buIk and weight}

The ferromagnetic body is formed by suspending com- m minuted sohd particles of a material having high magnetic susceptibility such as iron and similar ferromagnetic elements and compounds, including solid solutions of metal oxides (e.g. ferrites), m a suitable vehicle, preferably a non-conductor. The vehicle may comprise a highly volta- 55 tile component which, upon evaporation, leaves a lattice of magnetically permeable material; a hardenable compound (e.g. paraffin or a chlorinated wax) adapted to form upon curing a solid or semi-solid carrier where n the magnetically permeable particles remain suspended 60 a thixotropic material, such as a polyamide resin to an alkyd vehicle acting similarly upon setting; or a liquid ( .g. chlorinated naphthalene) in which the magnetically permeable material is maintained in suspension bu suiri able agitation.

, ^Tbe,^P,^artlcl“ ^of magnetically permeable material, which s ould be sufficiently small to penetrate completely the spaces in and around the coil (including its inter-turn ®^pac“’t,^lf3^{any) t0}J^mP^!'.^OTe the efficiency of the device, vibration or magnetic oscillations to achieve suitable par2 ίίν^ϊΐηΗΓ .^Furth®^rmor_e, the particles may be oriented ffiwfficS n ft ^{a masnetic field} while the vehicle n which the particles are suspended is still in a liquid or sur“dffiith^ate'-iYh°^{n S01idificaii0n of} the substance oriented potions ’ ^Ρ“ * ^{fixed in their}nartX^rdwV° ^{StU1 an}°^{ther featUre of the} invention, the 5 ^h°^{Se aVerage diameter} may range between and 20 microns, are suspended in a preferably organic non-conductive vehicle in the liquid state. The non-com ^ductlve vehicle, which may be a thermosetting or thermoP astic resin, serves to insulate the particles from eTch other electrically. The coil may thus be “potted” in a to avffid th??^{6 f}°J ^pr_f^Ot®^cti°^{n fr}°^{m physic£d im}P^{act and}personnel ΐί θί electrical shocks to maintenance personnel.. Thermosetting resins suitable for the present invention include epoxy resins and polyesters polymerized orSaK. ^lntr°^dUCed’ ^Senerally’ ^with ^a hardenffiT »

The above and other objects, features and advantages ent fromX f&lt;flrⁿ-^IOn7^iU-^{beCOme more read}ily applrtn it, ^folloW!ng description, reference being made ^t0 th® accompanying drawing in which:

FIG. 1 is an axial cross-sectional view of a mold for ^{25 a} tF^ansformer embodying the invention· ^F V; ^{2 1S},^{a VKW} Similar to FIG. 1, showing the com^ple*e^d transformer removed from the mold;

FIG. 3 is an axial cross-sectional view of a mold for . Ssi? - FIG. 4 is a side-elevational view, with parts broken ^aWFIC°5 -^he f°^mple.^{ted rela}y removed from the moffithe feld coik *^ont-^elevational view, partly in section, of FTC / ! ^m°^{tOr acc}°r^dmg to the invention;

’ broken avvay;¹¹ °^{f devke of FIG}· ⁵ P^a* FIG. 7 is a side-elevational view, with parts broken : ^aWpTC^Of8^{an ar}_f^matl,I'e ^for the motor of FIGS. 5 and 6· _^ρΙθ· 8 is a front-elevational view, partially in section ^structure embodying the’ ^{a pers}P^ective view, with parts broken away ^,he (e¹ u ^{tUbS 1} °^{f ferr}°magnetic material ie._o. sheet non) which serves as a mandrel for several primary and secondary transformer coils 4 these coils sSh““Η¹™”⁷ ~^d upon the mandrS andΐ sniped from one another by a non-conductive intervening layer 5 e.g. of oiled parchment paper. Spaced aneu larly at both ends of the tube 1 are channel^TfcrnS by bending flaps 3 outwardly, which serve to establish communication between the inner cavity of the shell and the surrounding regions. Flaps 3 serve to position the the en-i^{aXIa Iy}m¹⁰°^{8 the mandrel and} in the mold in which the coil assembly is placed. The mold consists of a kS member 10, sides 12 and a top 8, co-operating to form latter fuXr°^{mPletely enclosin}S ^{the coil} assembly. The ^ther comprises a transformer base 6, of a nonX pn f^Ve, ™^ateI^lal ^such as fiber-board sheet, carrying ne contact pins 7 of the transformer. The leads of coils 4, which are preferably wound from enameled copper wire, terminate in the pins 7. The transformer bare 6 ed^Pe°o^Vf th ^an.^{annuIar groove} in which the lower ⁵ 7™ ^f 7 ^{1 1S Seated}’ ^and with an inwardly tapermg aperture 66 opening into the inner cavity of the tubThe lower member 10 of the mold is provided with holes 11 receiving the pins 7.

are settled to any desired degree by‘the“use of mechanical ?θ netiSlv n!? ^pr°^yided ™^{th a} P°^{rt 9} for injecting the magvibration or magnetic osriUntinn. _____. .¹ . n^etlcally permeable substance into the mold. This substance comprises a ferromagnetic material preferably com3,201,739 minuted to a particle size of 5 to 20 microns and admixed with a suitable liquid vehicle. The vehicle may be a thermoplastic substance, liquefied by heat, or a polymerizable substance mixed with a hardener or catalyst prior to charging-the mold. While the comminuted ferromag· netic material is preferably suspended in the vehicle before the charge, it is also possible to add the ferromagnetic material to a mold previously filled with the vehicle.

The liquid charge is introduced into the mold through port 9 with an injection pressure of, advantageously, 1 j to 10 kg. per square centimeter to force the magnetically permeable substance into the cavity of tube 1 and thence, via channels 2, into the region surrounding the coils 4, so as to distribute itself about the latter and to penetrate throughout the mold cavity. The material also enters the aperture 6b, Upon setting, the magnetically permeable material, shown with stippled cross-sectional, hatching in FIG. 2, forms a core within the coil cavity which is linked, in a magnetic circuit, via the material in channels 2 with the material surrounding and encasing the coils 4. A portion 13α of the hardenable material, setting in the aperture 6b, interlocks the base 6 with the transformer. The vehicle may be cured in a number of ways. In the case of a thermosetting resin such as an epoxy, or polyester resin polymerized in — --------be cured by heating in an oven or by applying a highfrequency electric current to the coils to produce a heating effect.

A particularly suitable magnetically permeable substance may be formed according to the following example:

Example grams of an iron powder containing 14% silicon is mixed into a vehicle comprising 18 grams of diallylphthalate, 1.9 grams of styrene and 0.1 gram of cyclohexanone peroxide. The magnetically permeable substance, heated to a temperature of 30° C., is introduced into the mold through port 9 while the coils 4 are main' tained at a temperature of approximately 50° C. by resistive or inductive heating. The resulting transformer has been found to differ from conventional transformers of like rating by exhibiting an increase in heat dissipation of 7 to 12% due to the intimate contact of the coils 4 with the magnetically permeable material 13, a gain of. 11% in the weight of copper which may be used in the same volume, and a saving in bulk amounting to 7% when compared with stripped laminated transformers and to 17% as against shielded ones.

In FIG. 3 we show a mold for forming a relay of the telephone type, comprising a lower member 20, side members 22 and an upper member 18. A coil 14 is wound about a mandrel la, as previously described, and positioned in the mold. The relay base 16, adapted to carry the contact pins 15 of the relay, is provided with a tapered aperture 16&amp; adapted to interlock with the hardened magnetic material forming an inner core 14' and an outer shell 27, thus joining the base to the relay. The lower member 20 of the mold is provided with bores 21 receiving the pins 15. Coil 14 is provided with a copper ring 17, at its bottom, adapted to delay the release of the relay as is well known per set, and with a protective annular disk 17α along its top. The upper member 18, which is provided with an injection port 19, is formed with an annular shoulder 18α adapted to abut the disk 17α to isolate the upper part of core 14' from the shell 27, thereby forming an air gap 25 (FIG. 4) in the flux guide surrounding the coil 14. The magnetic material constituting this flux guide may comprise 90% by weight of a pure iron powder, 6% of a phenolic resin and 4% of a polyamide hardener for the resin. One of the side members 22 of the mold may be provided with recesses 22α, adapted to form ears 23 on the completed relay shown in FIG. 4, and 22b, adapted to form a flat boss 24 to which the switch contacts 26a, fastened between insulating blocks resin sucu as an cuuxy ui - —— -- ---------- * - - .__, in situ within the mold, the resin may 25 a hardenable magnetically permeable material of the char- - y 1 _ _ _ — f 1__J 'T'l— _Λ ττ,λ,ί.-3 1 ο ΛΗΓΌΟΟη νπ ΧΧ7ΤΩΤΊ—

26b, may be secured. The relay, upon being removed from the mold, may be provided with an armature 26 which is pivoted to the body of the relay at ears 23 and adapted to operate the contacts 26α. A magnetic field, induced in core 14' by the passage of an electric current through coil 14, serves to attract the armature 26 from its dot-dash position into its solid-line position in which it bridges the air gap 25 and, as illustrated, opens the normally closed contacts 26α.

In FIGS. 5 and 6 we show the field coils 31 of a motor, set in a mass of hardenable magnetic material. The leads of the coils 31 are connected to terminals 32, imbedded in this material. A cylindrical cavity 33, adapted, to receive a motor armature for free rotation therein, is provided in the flux-guiding body during casting or by subsequent machining. Slots 34 partially surround the coils 31 and the cavity 33 to define poles 28 Which concentrate the magnetic flux upon a suitable armature, for example of the type shown in FIG. 7. The magnetic circuit is completed by the outer branches 30 of magnetically permeable material which interconnect the breech portions 29 of the poles at the rear of each coil.

Tn FIG. 7 we show an armature for the motor in which a shaft 49 and a coil-suporting body 39 are formed from acter described. The pre-wound coils, encased in wrappers 35 which may be of lacquered fabric preferably haying sufficient resiliency to compensate for differences, in thermal expansion between coil and magnetic material, ; 30 are imbedded in this material, as are the commutator segments 37 which are connected to the leads 36 of the coils and constitute the terminals thereof. An insulating ring 38 abuts the commutator segments 37 on shaft 40. Generator armatures may be similarly constructed.

i It will be readily apparent that other accessories not related to either the electrical or the magnetic circuit may be mechanically secured to the body of the device. In this category fall cooling fans adapted to be imbedded in the shaft 40 of the commutator armature shown in FIG.

7, pump impellers which may be cast integral with the shaft, and turbine blades serving to drive the armatures of generators. The hardened magnetic material herein described is sufficiently strong to support a load.

In FIG. 8 we show a plurality of coils 41, 41', 41 45 carried on a perforated flexible mandrel 42 of ferromagnetic material bent into a toroidal shape and encased in a magnetically permeable substance 43 which enters through the perforations into the inner cavity 44 of the mandrel to form the core of the toroid. If the toroid is 5θ part of a magnetic amplifier, each set of coils 41, 41' and 41 forms a respective winding whose leads are connected to corresponding terminal sets 45, 45 and 45'. Similarly, a mandrel 52, carrying spools 51, may be wound into a helical configuration and potted in the magnetically 55 permeable material 53 as illustrated in FIG. 9. Each winding of the helical magnetic amplifier thus constituted is provided with a set of terminals 55, 55'. The helical configuration affords a more compact arrangement of magnetic amplifiers with large numbers of long windings θθ in a comparatively small unit. The magnetic circuit is completed through the external shell portion of the cast flux guide which communicates with the core of the coils at either end thereof, and/or at intermediate perforations in the mandrel 52.

The coils of any of the structures described and shown may, if desired, be enveloped in a resilient wrapping as set forth in connection with FIG. 7.

The pole strength of the relay shown in FIG. 3 and of the field-coil body shown in FIG. 5 may be materially ⁷⁰ increased by orienting the particles magnetically before the setting of the liquid vehicle in which they are suspended. A magnetic field applied externally, or internally by electrically energizing the potted coils, may be used for this purpose. A constant magnetic field may be used' ⁷⁵ to produce a core which is permanently magnetized when

3,201,729 the ferromagnetic particles are of magnetically retentive (e.g. ceramic) material. The particles may also be settled by mechanical vibration or magnetic oscillations, e.g. to permit introduction of further particles into the liquid vehicle from without to increase the density of the magnetic mass.

The invention described and illustrated permits of many modifications and variations believed to be within the ability of persons skilled in the art, and intended to be included within the spirit and scope thereof, except as further limited by the appended claims.